One of the most powerful results of recent advances in graphics hardware is the ability of a computer user to interactively explore a virtual buildin gor landscape. The newest three-dimensional input devices, together with high speed {3D} graphics workstations, make it possible to view and move through a {3D} scene by interactively controlling the motion of a virtual camera. In this paper, we describe how natural and intuitive control of building walkthrough can be achieved by using a physically-based model of the virtual camera's behavior. Using the laws of classical mechanics to create and abstract physical model of the camera, we then simulate the virtual camera motion in real time in response to force date from the various {3D} input devices (e.g. the Spaceball and Polhemus 3Space Digitizer). The resulting interactive behavior of the model is determined by several physical parameters such as mass, moment of inertia, and various friction coefficients which can all be varied interactively, and by constraints on the camera's degrees of freedom. This allows us to explore a continuous range of physically-based metaphors for controlling the camera motion. We present the results of experiments using several of these metaphors for virtual camera motion and describe the effects of the various physical parameters.
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